Air brake and other auxiliary systems requiring compressed air are known for tractor/trailer vehicles. In conventional tractor/trailer vehicles, the basic air system components include an air compressor with a governor valve, an air dryer, a supply reservoir tank, valves for controlling flow of the compressed air to the brake and other auxiliary systems, and wheel mounted brakes and brake chambers. In an air brake system, for example, the compressor furnishes the compressed air for brake operation by compressing atmospheric air.
Typical air brake systems have operating pressures of between 95 psi and 135 psi. If the air brake system compressed air pressure does not reach the system operating pressure or is slow to reach the system operating pressure, the air compressor is generally tested for issues first. There are known expensive and complicated devices for testing the output of the compressor. The other components in the air charging system, such as the discharge line from the compressor or the air dryer, are generally not tested with the expensive test devices, but may be the true cause of the system not building air. Some technicians without the proper tools or diagnostic training may choose to assume that the compressor is faulty and undergo the labor intensive project of removing the compressor from the vehicle for warranty service.